Metal-insulator-metal (MIM) capacitors are valuable components in memory, logic and analog circuits. For example, MIM capacitors are critical in several mixed signal integrated circuits such as analog frequency tuning circuits, switched capacitor circuits, filters, resonators, up-conversion and down-conversion mixers, and A/D converters.
A typical MIM capacitor includes a first conductive layer, an insulating layer formed over the first conductive layer, and a second conductive layer formed over the insulating layer. As constructed, a MIM capacitor can store an electrical charge, with the charge per applied voltage (capacitance) of the capacitor dependent on the dielectric constant of the insulating layer, the thickness of the insulating layer (i.e., distance between the faces of the conductive layers), and the area of the conductive layers.
Typically integrated circuits also include resistors. Conventional resistors include doped polycrystalline silicon (polysilicon) resistive elements patterned to form a desired geometry. Contacts are formed at opposite ends of each doped polysilicon resistive element, such as from patterned silicide patches. The contacts define a conductive path to the doped polysilicon resistive elements and facilitate integration of the resistor with other semiconductor structures.
Resistors trued from doped polysilicon resistive elements typically suffer from high variability in resistance. For example, the resistance of resistors formed from doped polysilicon resistive elements may vary because of non-uniform hydrogen penetration into the polysilicon. Further, the resistance may vary due to the non-uniformity of doping processes. The resistance variability of resistors is a key concern in analog and digital circuit design.
Resistors formed from metal typically exhibit more precisely defined resistance. However, use of metal resistors in integrated circuits increases processing steps. Specifically, the formation of metal resistors typically requires additional mask deposition, patterning, and removal processes. As a result, overall integrated circuit fabrication processing cost is increased.
Accordingly, it is desirable to provide integrated circuits and methods for fabricating integrated circuits having resistor structures with more precisely defined resistance. Also, it is desirable to provide integrated circuits and methods for fabricating integrated circuits with resistor structures formed from a material other than polysilicon, e.g., MIM capacitor material. Further, it is desirable to provide methods for fabricating integrated circuits with resistor structures using no additional masking processes. Furthermore, other desirable features and characteristics will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.